How to drill

an ice shelf

— and why

Christmas Day 2023. While many of us are at the beach or around the barbie, a plucky team of four scientists and a polar field guide pitch their tents at what must be the world’s most remote campsite: the Shackleton ice shelf.

Almost nothing is known about this massive system of interlocking ice shelves and glaciers in East Antarctica, around 5,000 kilometres south of Australia.

Ice shelves are floating edges of the ice sheet that fringe three-quarters of the Antarctic coast. They act as ‘seat belts’ to restrain ice on land from flowing into the sea and causing sea level rise. Without them, glaciers could slip into rapid retreat.

This is the story of how (and why) Sarah, Madelaine, Katie, Duanne and Nick drilled a hole through the Shackleton ice shelf to reach the ocean — and what they found beneath.

Shackleton ice shelf (video: Sarah Thompson)

Shackleton ice shelf (video: Sarah Thompson)

Antarctica’s ‘soft underbelly’

The Antarctic Ice Sheet holds 70% of Earth's freshwater and 90% of our planet’s ice.

The kilometres-thick dome of frozen snow flows inexorably to the sea through glaciers. 

Suspended in that ice sheet, if it all melted, is about 58 metres of potential sea-level rise.

Most of Antarctica’s ice is stored in the East Antarctic Ice Sheet, with enough to raise global sea level by around 52 metres — over four times greater than both Greenland and West Antarctica combined.

Antarctica’s coastal fringe is its key point of vulnerability. This is where the floating extensions of the land ice, known as ice shelves, buttress the ice sheet on land and slow ice flow into the sea. 

But if ice shelves are eroded by warmer waters, they can melt and disintegrate faster, allowing the flow of land ice into the ocean to accelerate.

Ice shelves are Antarctica’s soft underbelly, their stability at the mercy of changes in the Southern Ocean.

Paleo Nim (CC BY-SA 4.0)

Paleo Nim (CC BY-SA 4.0)

The Shackleton 'seat belt'

The 110-kilometre-long Denman Glacier drains a vast area of the East Antarctic Ice Sheet.

Before it reaches the sea, the Denman Glacier flows through a canyon about 3.5 kilometres below the surface, making it the deepest known glacier on Earth.

This is largely unknown territory.

The Denman Glacier tongue floating on the ocean is surrounded by the Shackleton ice shelf.

At about 34,000 square kilometres, the ice shelf covers more than half the area of Tasmania.

The massive Shackleton ice-shelf system is a traffic jam of smaller glaciers and ice tongues that slows the flow of ice from the interior to the ocean.

Shackleton is the most northerly ice-shelf system outside the Antarctic Peninsula.

So the discovery of Antarctica’s deepest subglacial trough beneath the Denman Glacier — combined with high melting rates and the southward advance of warming ocean waters — raises alarm bells about its vulnerability to accelerating retreat.

Denman-Shackleton system 2020 (photo: NASA Earth Observatory/Joshua Stevens)

Denman-Shackleton system 2020 (photo: NASA Earth Observatory/Joshua Stevens)

Meet the crack team

L-R: Madi, Sarah, Katie and Nick fly in to field camp (photo: Madi Rosevear)

L-R: Madi, Sarah, Katie and Nick fly in to field camp (photo: Madi Rosevear)

The fate of the Denman glacier depends a lot on the future stability of the Shackleton ice shelf. Knowing more about the oceanographic conditions under the ice shelf will improve predictability of the emerging risks from warming waters.

That’s the point of this mission, says glaciologist and team leader Dr Sarah Thompson of the Australian Antarctic Program Partnership at the University of Tasmania.

“Before we went to the ice shelf, we didn’t even have much of an idea how deep the ocean floor was.”

“Although critical to understanding ice shelf stability, measurements underneath ice shelves are very difficult to get and therefore rare.”

Which is why oceanographer Dr Madelaine (Madi) Rosevear from the Australian Centre of Excellence for Antarctic Science (ACEAS) and the University of Melbourne is part of the team.

“Most of my experience collecting ocean data has been working through holes in sea ice or ice shelves, which has unique challenges, like the tendency for ice to affect sensors in weird and wonderful ways.”

“There are only a handful of measurements of the ocean beneath ice shelves in Antarctica, and none for the Shackleton ice shelf.”

Glaciologist Dr Katie Miles from Lancaster University has experience in driving the drill technology that uses hot pressurised water to melt a hole through the ice shelf.

Katie Miles (photo: Sarah Thompson)

Katie Miles (photo: Sarah Thompson)

Nick, Madi and Katie at the drill head (photo: Sarah Thompson)

Nick, Madi and Katie at the drill head (photo: Sarah Thompson)

Associate Professor Duanne White is a geomorphologist from the University of Canberra who analyses sediment from the sea floor to interpret the past — and potentially future — behaviour of the ice sheet.

As an experienced polar field guide, Nick Morgan from the Australian Antarctic Division is central to getting the work done safely and efficiently. He does a lot of the digging, drilling and refuelling as well as helping with the instrument deployments.

Nick surrounded by pumps (photo: Sarah Thompson)

Nick surrounded by pumps (photo: Sarah Thompson)

Duanne with a sediment core (photo: Sarah Thompson)

Duanne with a sediment core (photo: Sarah Thompson)

Life on the ice

The team lived in their field camp on the Shackleton ice shelf for four weeks.

“Camping on an ice shelf is always an incredible and sometimes surreal experience. Every now and then you look up and remember just where you are,” Sarah says.

“Nobody has ever been here before, let alone camped here for a month.”

“All of the things that people think will be challenging — like no showers, having to melt all your water for drinking and having a bucket for a toilet — very quickly become routine.”

One of the main challenges, says Sarah, is that the longer you camp in a particular place, the more the snow melts underneath you.

“This doesn’t happen in a uniform way and so every single surface is at a different angle. You have to be careful that your morning coffee doesn’t slide off the table, and using the toilet bucket definitely required more balance later in the season.”

Life at Camp Shackleton was dominated by wind and snow.

“We had several blizzards where we needed to dig out all of the tents multiple times a day and then excavate all of the equipment before we could start drilling again,” sighs Sarah.

Madi brought to camp what she describes as a “generic Antarctic fieldwork skill set.”

“Things like knowing good knots, creative ways of shifting heavy objects, cold and fatigue management, and a good sense of humour."

Digging tents out after another heavy snowfall (photo: Sarah Thompson)

Digging tents out after another heavy snowfall (photo: Sarah Thompson)

Madi is snowbound

Madi is snowbound

The gentle art of

hot water drilling